1. Field of the Invention
The present invention relates to improvements of a semiconductor flow velocity sensor for electrically sensing the velocity of fluid flow.
2. Description of the Prior Art
There is well-known a semiconductor flow velocity sensor comprising a semiconductor substrate and a heating unit on the substrate. Such a sensor is currently used to measure the flow velocity of gaseous or liquid fluid since it can electrically sense the heat transfer from the heating unit which varies depending on the velocity of fluid flow.
In the prior art, however, the silicon substrate and heating unit are not thermally isolated such that the mounts of the sensor and associated substrate will function as thermal loads having a large heat capacity relative to the heating unit. Therefore, measurements cannot accurately be made with a good response time.
Silicon is a very highly thermal conductive material. Therefore, if a heating unit is disposed on a silicon semiconductor substrate, the silicon semiconductor substrate will entirely be heated. In such a situation, peripheral sensor circuits, which are similarly made of semiconductors sensitive to changes in temperature, cannot be located on the same semiconductor substrate on which the heating unit is disposed. This prevents the sensor from being more integrated.